Paperless cigarette filter and apparatus for manufacture thereof

ABSTRACT

AN IMPROVEMENT IN MANUFACTURING EQUIPMENT FOR MAKING PAPERLESS CIGARETTE FILTER RODS. A CIGARETTE FILTER ELEMENT COMPOSED OF A COMPACTED BUNDLE OF CELLULOSE ACETATE FILAMENTS CHARACTERIZED BY A UNIFORM POROSITY AND A SMOOTH SURFACE IS OBTAINED BY THE USE OF SUCH APPARATUS. THE APPARATUS COMPRISES: (1) A WEB GATHERING MEANS FOR COLLECTING AND DIRECTING A WEB OF PLASTICIZED FILAMENTARY TOW INTO A ROD COMPACTION MEANS FORMED BETWEEN THE SURFACE OF A SERIES OF OPPOSITELY ROTATING STEAM INJECTING WHEELS, (2) A ROD-SHAPING MEANS FORMED BY THE COOPERATIVE CORRESPONDENCE OF THE OPPOSED SURFACES OF A CONTIGUOUS PAIR OF PERIPHERAL GROOVES LOCATED IN THE OPPOSING SURFACES OF AT LEAST ONE PAIR OF CO-ACTING OPPOSITELY ROTATING APERTURED WHEELS, TO FORM A DIE FORM, (3) A MEANS FOR INJECTING A HEATING FLUID DIRECTLY INTO SAID ROD-SHAPING MEANS THROUGH ITS APERTURED WALLS WHILE THE CONTENTS OF THE ROD-SHAPING MEANS ARE UNDER COMPACTING PRESSURE   AND THE ROTATING WHEELS ARE IN MOTION, (4) A MEANS FOR DRYING, COOLING, AND CONSEQUENTLY CURING THE PLASTIC RODSHAPED PRODUCT OF THE HEATING AND COMPACTING ACTION OF THE DIE. THE MEANS INDICATED BY (4) MAY BE A SECOND PAIR OR PAIRS OF GROOVED APERTURED WHEELS CONNECTED TO AN AIR SUPPLY OR MAY COMPRISE A CYLINDRICAL ENCLOSED PLENUM CHAMBER CONTAINING THEREIN A FORAMINATED CENTRAL TUBE THROUGH WHICH THE ROD OF HEATED TOW PASSES. THE PASSAGE OF AIR INTO THE PLENUM CHAMBER CAUSES AFLOW OF AIR TO CIRCULATE ABOUT, COOL, AND AIR CURE THE SURFACE OF A FILAMENTARY ROD PASSING THROUGH THE CENTRALLY LOCATED TUBE. THE CURED ROD IS SUBSEQUENTLY SEVERED INTO MEASURED SEGMENTS OF CIGARETTE FILTER ROD ELEMENTS HAVING ENHANCED STRUCTURAL INTEGRITY AND REQUIRING NO PAPER OVERWRAP DURING MANUFACTURE.

n 6 1971 c s. M ARTHUR ETAL 3,560,393

PAPERLESS CIGARETTE FILTER AND APPARATUS FOR MANUFACTURE THEREOF .Filed July 30, 1968 3 Sheets-Sheet 1 INVENTORS COLIN S. MCARTHUR BY How 5. BEARD JOHN R. EVERHART ATTORNEY Feb. 2, 1971 c. s. M ARTHUR ETAL 3,560,298

PAPERLE CIGARE AND APPARATUS TTE FILTER R MANUFACTURE THEREOF Filed July 30, 1968 3 Sheets-Sheet 2 C S. M ARTHUR ETAL PAPERLESS CIGARETTE FILTER AND APPARATUS FOR MANUFACTURE THEREOF Feb. 2, 1971 3 Sheets-Sheet 3 Filed July 30, 1968 United States Patent US. Cl. 156-376 4 Claims ABSTRACT OF THE DISCLOSURE An improvement in manufacturing equipment for making paperless cigarette filter rods. A cigarette filter element composed of a compacted bundle of cellulose acetate filaments characterized by a uniform porosity and a smooth surface is obtained by the use of such apparatus. The apparatus comprises: (1) a web gathering means for collecting and directing a web of plasticized filamentary tow into a rod compaction means formed between the surface of a series of oppositely rotating steam injecting wheels, (2) a rod-shaping means formed by the cooperative correspondence of the opposed surfaces of a contiguous pair of peripheral grooves located in the opposing surfaces of at least one pair of co-acting oppositely rotating apertured wheels, to form a die form, (3) a means for injecting a heating fluid directly into said rod-shaping means through its apertured walls while the contents of the rod-shaping means are under a compacting pressure and the rotating wheels are in motion, (4) a means for drying, cooling, and consequently curing the plastic rodshaped product of the heating and compacting action of the die. The means indicated by (4) may be a second pair or pairs of grooved apertured wheels connected to an air supply or may comprise a cylindrical enclosed plenum chamber containing therein a foraminated central tube through which the rod of heated tow passes. The passage of air into the plenum chamber causes a flow of air to circulate about, cool, and air cure the surface of a filamentary rod passing through the centrally located tube. The cured rod is subsequently severed into measured segments of cigarette filter rod elements having enhanced structural integrity and requiring no paper overwrap during manufacture.

BACKGROUND OF THE INVENTION Cigarette filter elements which employ a tow or bundle of several thousand cellulose acetate filaments arranged in a porous rod-shaped slug or segment have achieved a dominant position in the manufacture of filter type cigarette products. As presently employed, these elements have the advantage of ready adaptation to crimping of the thermoplastic filamentary constituents coupled with an added capacity for compatible bonding of the fibers with each other in the presence of an activating or plasticizing agent.

In a common practice of manufacture of such rodshaped elements, a tow of cellulose acetate filaments is worked into a web or mat of such filaments which contains thousands of individual filaments of varying degrees of cross-sectional diameter. The cross-sectional diameter of the tow employed Whether cut or continuous, is related 3,560,298 Patented Feb. 2, 1971 to the degree of stretch applied to the individual filament. In general, the denier of the individual filament runs from 2 to about 12 denier. This filamentary bundle of tow is normally sprayed with a known plasticizing or bonding agent such as dibutyl phthalate, triethyl citrate or the like to soften the filamentary material in preparation for subsequent compaction and bonding of the fibers into a rod. The web of plasticized tow is then condensed by passage through a conical device resembling a trumpet which has a diminishing conduit extending between an entrance orifice of greater diameter and an exit orifice of reduced cross-sectional diameter. At this point, the filamentary tow reduced to a continuous rod-like shape of predetermined cross-sectional diameter is wrapped in a paper cover to lend reinforcement for the wet bundle of filaments, and cured either before or after being cut into short measured segments.

This overwrap is usually done by means of the use of one of a number of conventional cigarette wrapping Inachines which surround the fibrous bundle with a paper wrapping. The paper wrapped filter rod is then segmented into short elements of the order of 20 to millimeters in length and subjected to curing by one of several techniques. In a typical technique, the rod-shaped filter elements are heated to a temperature of from 180 F. for from 1 to 2 hours to spread and activate the plasticizer and insure a firm joinder of the crimped filaments. The final step of the cure involves a cooling and drying step to fix the bond of the binding agent among the mass of crimped filaments. The conventional means for the curing step is either an accelerated cure at chilled dry room conditions or room temperature curing which requires a longer cure time. In any event, the filter rod is ultimately employed in a cigarette manufacturing process and incorporated with an individual cigarette by means of a tipping overwrap usually composed of paper.

If one proceeds along the technique of manufacture outlined above, the wrapping in paper of each filter element prior to cure becomes time and material consuming and in large scale filter cigarette manufacture, also quite costly. It therefore became an object of inventors in the art to develop a paperless cigarette filter rod. US. Pat. 3,190,294 to Dunlap illustrates one such early attempt at preparing shape retaining paperless cigarette filter plugs which involved heating and forming a surface hardened filter rod. In the Dunlap method, the patentee employs as his forming or shaping die a pair of opposed rotatable heated grooved rollers which cooperate to form a die cavity through which the plasticized tow is passed for both compaction of the fiber bundle and heating and hardening of the surface layer of cellulose acetate filaments. The heating of the filamentary tow being shaped in Dunlap is affected by electric heating elements implanted in the walls of the die cavity which heat the surface of the rod of tow passing through by conduction of heat at the points of contact. To be sure a paperless cigarette filter element is obtained by this technique, but it is difficult to achieve a maximum uniform internal porosity of the fibrous contents of such element. This problem is compounded in Dunlap due to the :fact that the shaped rod has had a surface fiber congealing heat applied but no means for internal injection of a heating fluid to partially cure and separate the internal fiber bonds which occasionally aggregate together in uneven patterns.

A later method and equipment for manufacture of paperless self-sustaining cellulose acetate cigarette filter elements is disclosed in Berger et al. Pat. 3,313,306 which suggests the use of an endless belt carrier for rod-forming filamentary tow and involves conducting the tow and belt through a restrictive tube bore with the tow contained within the belt. A treatment with steam will infuse the belt to activate the fibrous tow therein while the belt simultaneously compresses the tow into a rod of uniform crosssectional diameter. With the use of this technique, the treating steam must pass through the surrounding carrier belt and does not impinge directly and proximally upon the tow to insure maximum penetration. The carrying belt moreover frequently does not fit perfectly around the confined tow it carries and being subject to wear and maintenance difficulties under continued operations presents practical operating ditficulties.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is the provision of a method and apparatus for rapidly condensing a fibrous bundle of cellulose acetate filaments into a shaped porous rod which maintains its surface porosity yet has sufificient rigidity to render the rod selfsustaining.

A collateral object of the invention is to provide an apparatus means for simultaneously heating with a penetrating jet of steam a bundle of cellulose acetate filaments at the same instant the filaments are being compressed within the confines of a die form. A further object is to attain a continuous filter rod with a smooth hardened porous surface area and uniform internal porosity.

Another object is to provide a means for immediately drying and cooling the heated porous rod formed within the confines of the die so as to cure the surface of the rod while it is still wet and warm.

A still further object of the invention is the provision of novel apparatus means for attaining these objectives which has a minimum of maintenance problem and is capable of rapid processing of filamentary tow into cigarette filter rod elements. Other objects of the invention will become apparent from a consideration of the detailed description of the invention.

SUMMARY OF THE INVENTION In accord with the present invention, an improved apparatus for the manufacture of paperless cigarette filter rods is presented. By the terms paperless filter rods or elements as they are understood in the art we refer to those segments of shaped and bonded thermoplastic filaments frequently composed of cellulose acetate material which do not require a separate paper overwrap to hold them together while they are being bonded and cured. Cigarette filter rods of this type are rapidly produced at diminished manufacturing cost due to the presence of this attribute. The quality control over such products is excellent in view of the fact that the entire surface area of such rods is visible during the production thereof even under high speed production schedules.

The general method of manufacture of paperless cigarette filter elements to which the present apparatus improvements pertain is comprised of the following sequence of filamentary treatment operations. First a mass of filamentary tow is worked into a thin web of generally longitudinally aligned thermoplastic filaments by carding equipment and passage through a picker machine. If desired at this point, the web may be treated with a plasticizing agent by spraying the web with a suitable agent of this type to swell the individual filaments. This plasticized web of filamentary material is next passed through a cone shaped tube or conduit which forms the web of filaments into a more condensed mass. Various shaped condensing tubes may be employed with the only common characteristic between them being that the entrance orifice is larger than the exit orifice.

The plasticized impregnated tow is then passed from the exit orifice of the condenser tube into a die or opening defined between the surfaces of at least two contacting peripherally grooved oppositely rotating wheels or discs. At this point, the plasticized tow is compressed from all sides and compacted into a rod of predetermined size and shape. At the same time, this compression is taking place, heated wet steam is forced into the filamentary mass while it is under compression. This steam issues from a series of steam jets which line the peripheral grooves of the rotating wheels or discs. The infusion of fluid into the fiber mass under simultaneous compression causes two things to occur at this point:

(1) The filaments within the center of the mass are maintained in partial contact uniformly by the injected steam and move out to entirely fill the internal area of the die cavity. This prevents any localization or clumping of fiber filaments in any given area of the filamentary mass under compression;

(2) The plasticized filaments near the surface begin to cure and soften because of the action of heat from the steam which enters the tow from a plurality of directions simultaneously.

From the compression and steam activation stage, the compressed wet rod of tow passes immediately into a cooling and drying chamber. In this chamber cool dry air enters and circulates through a plenum chamber positioned to surround a central tube or conduit through which the hot compressed porous rod is caused to pass. This central tube contains a multitude of perforations therein for passage of air from the plenum chamber into direct circulatory contact with the heated compressed rod. As the circulating cool air in the plenum chamber strikes the surface layer of fibers in the rod, it chills these and accelerates their rate of stiffening or loss of thermoplasticity. The filamentary porosity of the fibers in the center of the rod is maintained, however, as is that porosity in those fibers nearer the periphery of the rod although the fibers assume a more rigid condition.

In some instances where additional bonding is considered necessary, the process of steaming followed by cooling may be repeated. In any event, the continuous rod when cooled is cut into short segments for incorporation into cigarettes.

BRIEF DESCRIPTION OF THE DRAWING The novel apparatus of my invention which makes such unique processing possible will now be described in detail with reference to the accompanying drawing, wherein:

FIG. 1 is a perspective view of the apparatus which applicant claims as his invention;

FIG. 2 is a fragmentary plan view of the compacting and steam injection wheels which coact to simultaneously shape and steam inject the bundle of filamentary tow passing therethrough;

FIG. 3 is a cross-sectional view of the same compacting wheels taken along line 33 of FIG. 2 to more specifically show the means of steam contact with the tow while it is under compaction pressure;

FIG. 4 is a partially broken away perspective view of the air drying unit of the apparatus;

FIG. 5 is a diagrammatic view of a belt operated drive mechanism for the wheel apparatus of FIG. 1 viewed from the underside of said apparatus;

FIG. 6 is a schematic perspective view of a complete manufacturing system which includes the apparatus of the present invention oriented in the vertical plane;

FIG. 7 is also a schematic perspective view of an apparatus arrangement similar to that of 'FIG. 6 except that the apparatus is oriented horizontally and the air treatment station is clearly shown as a distinct station as illustrated in FIG. 1; and

FIG. 8 is a cross sectional view of the filter rod produced by the operation of the apparatus described above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the several figures of the drawing to more specifically described the invention, it will be noted for example in FIG. 1, there is shown in perspective view the apparatus assembly which makes up applicants unique means for simultaneous steam treating and compacting of a web of filamentary tow into a porous rigid paperless cigarette filter element. The crimped cellulose acetate web 1 is shown entering a tow guide 2 which condenses and leads it to the pulling nip between the first two oppositely rotating compaction wheels 3a and 3b. Each of these wheels are structurally identical and when their faces are contiguous they form a shaping die form 4. The movement of the condensed filamentary tow into this compaction zone is motivated by the synchronized controlled rotation of compaction wheels 3a and 3b held together by tension spring 5 and which wheels rotate about drive axis 7. Axis 7 is itself actuated by the controlled movement of endless driving belt 25 actuated by a belt driving wheel 26 and passing over an idler Wheel 27. When in the location illustrated as within the compaction zone shown in FIG. 2, the bundle or web of filamentary tow has in many cases already been permeated with a conventional plasticizer which has been added prior to forwarding of the web of tow to the rod shaping apparatus. Generally the feed of plasticized tow is controllably led into the nip between compaction wheels 3a and 3b as a web from feed rolls 30 of conventional design shown in FIG. 6. The speed of the compaction wheels is synchronized to be the same because of the common contact with the actuating belt drive.

An important element of the present apparatus is the die form 4 formed by the coming together of the peripherally grooved wheels 3a and 3b as is illustrated particularly in detail in FIGS. 2 and 3. By the correspondence of each contiguous face 6 of compaction wheels 3a and 3b, a cylindrical shaped die is made available for shaping a cylindrical rod of tow. This die form is continuously formed as the compaction wheels slowly rotate in opposi tion toward each other while their faces are forced together under the tension of spring 5 attached on either end of the spring to a mounting frame 8 for support of each wheel and through which the wheel axis 7 of each compaction wheels 3a and 3b is journalled. If a series of such compaction wheels are to be employed a series of matched pairs of spring compressed mounting frame elements of the same structure as frame 8 would of course be used in the exact same manner with each mounting frame connected laterally with a lateral connector rod.

Preferably as shown in FIG. 1, additional springs similar to spring 5 can be directly attached to the mounting frame as extended laterally. In any event, the face 6 of each wheel 3a and 3b each contains a centrally located concave peripheral groove 9 which when in exact contiguous relation to its opposite member on the other wheel defines a hollow cylindrical die form open at both ends and circumferentially closed. The die form 4 may be viewed as stationary at a fixed portion of wheel face 6 of both wheels with the concave surfaces of the peripheral groove forming the walls of the die. Into this form 4 at the instant it is formed wet hot steam is fed through a plurality of laterally opening steam jets 17 which open directly into the concave walls of the peripheral groove 9. Alternatively, the groove itself may consist of a ring of porous material of, for example, a ceramic or sintered material composition, such ring being fed from its inner surface by steam holes. By means of either of these arrangements, hot steam blasts of wet steam under a pressure of about 20 p.s.i.g. are directed at a segment of filamentary tow undergoing compaction in the die form. This hot steam, as can be appreciated from FIG. 3 of the drawing, impinges directly on the tow from a plurality of directions simultaneously and serves to permeate all sectors of its filamentary contents.

The particular significance of this structural improvement over the wheel die with imbedded electric heating elements shown in the prior art is that the permeating steam is able to penetrate and dechannelize the filamentary tow while it is being compacted. In addition, the impinging steam activates any plasticizer present and softens the individual filaments for subsequent bonding. Unlike the prior art manufacturing techniques, the present apparatus permits one to maintain a surface cure sufficient to afford the rigidity demanded of paperless cigarette filter elements yet enhances development of the internal porosity, filament separation, and surface smoothness of the rod being formed. By direct steam injection while com pression is simultaneously applied, our apparatus allows one to hold the filaments partially apart at the instant the rod is being initially surface cured and compacted. This specifically is what is referred to above as dechannelizing and such effect has been attained by our apparatus means as illustrated in FIG. 3, particularly to induce simultaneous cross-current steam impingment at the instant of compaction of the filamentary tow into a partially cured rod.

As illustrated in FIGS. 1 and 3 of the drawing, the steam injected into die form 4 is derived from a conventional steam generator (not shown) and is introduced through steam feed inlet 10. From there it proceeds through manifold 11 into steam feed conduit 12. Each of these steam feed conduits are supported on a mounting frame 13 to comprise a steam feed assembly. The steam feed conduits 12 come into register with steam inlet holes 15 in the lateral surface of each wheel as the wheel 3 turns on its axis 7. To insure a proper register and a tight fit between the steam feed conduits 12 and the steam inlet hole 15 a vertical compression spring 14 is attached on one end to an upper attachment pin 3-1 in the top of the steam feed assembly and on the other end to a second lower attachment pin 32 in the lower mounting frame 13 of the assembly. The mounting frame 13 of course is bound to rotating compactor wheel 3 through frame members not shown. This arrangement tends to force the steam conduit into constant contact with the wheel it is steam feeding. The input steam then proceeds into angular steam ducts 16 in the wheel which carry it to steam jets 17 which supply the steam directly into the die form 4. As previously stated, a porous metal ring may be used to form the die form 4 in which case the angular steam ducts -17 would furnish steam to the inner surface of said ring.

The steam heated, shaped, compacted rod 23 of filamentary tow is in a soft moist condition as it issues from the die form 4 formed by the correspondence of the surfaces of the compaction wheels 3a and 3b. By virtue of the movement of the compaction wheels, the tow is urged forward into an air drying station 19 specifically illustrated in FIG. 4 where it is dried and cooled by contact with a dry curing fluid preferably air. This air is introduced into the processing equipment through an intake line 18 and is caused to circulate within the drying station 19 in a plenum chamber 20 and into a central tow carrier tube 21 through which the wet hot tow rod 23 is conducted. The air in the plenum chamber 20 is dispersed in contact with the rod through a series of circumferential air contact ports 22. The unique manner of construction of the air drying station 19 gives to the emerging dried compacted rod 24 a characteristic partial coalescence of the surface filaments of the rod since these have been placed in contact with the curing cool dispersed air over the entire surface of the rod within the air drying station. As indicated by FIG. 1 this process of steam softening and subsequent air drying can be repeated several times if required by the condition of the rod desired to be produced.

In FIG. 5 is illustrated a diagrammatic View of a belt operated drive mechanism for the series of compacting wheels 3a, 3b etc. discussed hereinabove. This drive mechanism is actuated by a driving wheel 26 for the endless driving belt 25. The idler wheel 27 maintains the system in a continuous movement as the driving belt 25, which is preferably of a chain type contacts the sprocket rim 29 of each carrier wheel 28 and turns each wheel in synchronized rotation. By control of the rate of rotation of the carrier wheels 28, etc., the precise speed of rotation of the attached compacting wheels 3a, etc. is controlled since there is a direct communication of the motivating torque from the carrier wheels 28, etc. through the axis 7 to the compacting wheels 3a, 3b, etc.

FIG. 6 is a schematic perspective view of a complete manufacturing system for the production of paperless cigarette filters from a supply of filamentary tow. The starting tow may be any one of several thermoplastic materials currently employed for such use. In place of cellulose ester fibers such as cellulose acetate, such other fibrous materials as those derived from linear polyesters such as polyethylene terephthalate, polyamides such as nylon and other various thermoplastic fibers may be employed as tow. The tow treated can be either continuous filamentary tow or cut staple lengths of the same or mixtures of the two. The lengths of cut staple can vary between /2 inch to 4 inches and can be blended in varying ratios. As a general rule, the composition of the filamentary material employed will dictate the plasticizing agent of preference. Using cellulose acetate such agents as methyl phthalyl ethyl glycolate, glyceral triacetate, triethyl citrate and the solvents acetone, dimethyl formamide, methylene chloride and the like are preferred. In any event referring to FIG. 6 a layer of filamentary tow 33 is passed through a conventional opening device 34 which opens or tends to separate the individual filaments. The tow then passes over idler rolls 35 and through the nip of feed rolls 36 to a plasticizer treatment area where a conventional plasticizer is sprayed on the lap usually by application on both sides from plasticizer applicator 37. The plasticized tow then passes through fluffing device 38 where the layer of filaments are fluffed to form a loose bundle of filaments. The layer of filaments are fluffed to form a loose bundle of filaments. The layer of filaments is then usually reduced in thickness to about A; inch and is in the shape of a thin web. This web is passed over a pair of feed rolls 30 which direct the web of tow into the tow guide 2 of the present invention. The tow is then shaped and steam treated as described above and illustrated in detail in FIGS. 1 to 5. The finished rod of tow is cut into premeasured segments in cutter 39 and packaged and collected as finished product in the collector receptacle 40.

In the perspective view of the invention set forth in FIG. 7 the arrangement of the steam treating or curing station and the air treating or curing station are shown in relation to each other and the rest of the manufacturing system. It is within the general concept of the invention that additional steam can be introduced to replace air in curing station 19 if for some reason additional steam curing was needed in treating a particular resinous fiber or filamentary blend which requires a high softening temperature. In the same regard, if a more rapid air cure is needed for a particular plastic material an air jet arrangement similar to that shown as 15, 16 and 17 for steam injection can be substituted to replace the last set of foraminated compacting wheel steam heating elements. Any changes of this type would of course be expected to alter the properties of the porous filter rods produced since it will alter somewhat the dual uniform crosssectional internal porosity and external surface filamentary bonded characteristics of the ultimate rod-shaped article obtained.

The product produced as a result of the operation of the apparatus of the present invention is a tow in the form of a paperless shape-retaining cigarette filter rod as depicted in cross section in FIG. 8. The individual filaments of the tow in the rod are crimped and have an average denier of about 1.8 to 4.0.

The following example is set forth to illustrate a preferred mode of practice of the invention using the apparatus as described in FIGS. 1 through 7 above. The example is intended to be merely descriptive of the invention. For a legal definition of the scope of the inventive concept attention must be directed to the several claims appended hereto.

EXAMPLE A web of cellulose acetate having an individual denier per filament of 2.2 and an overall denier of 34,000 was plasticized by the addition of triacetin and conducted into a rod compaction means formed between the grooved surfaces of a series of paired oppositely rotating wheels having steam injection means therein. The steam was injected under a pressure of 30 p.s.i.g. at a temperature of 280 F. to simultaneously compress the filamentary tow into a filamentary rod while injecting the heated steam therein. Subsequently, the rod shaped bundle of filamentary tow was conducted into a cooling chamber constructed so as to comprise a plenum chamber containing a foraminated central tube through which the rod of heated tow passed. Cool air was introduced into the plenum chamber at a pressure of 10 p.s.i.g. and at about room temperature so as to circulate within the chamber, contact and cool the rod of heated tow passing through the foraminated tube. At this point the speed of the tow passing through the apparatus is approximately 570 feet per minute. After the rod had been cooled and hardened it was cut into a series of porous cylindrical rods of about millimeters in length and 7.65 millimeters in average cross sectional diameter.

These cylindrical porous rods were characterized by a uniform porosity throughout and a smooth surface area on the periphery thereof. Under normal operating conditions the process operates to produce about 1,450 filter units per minute. These filter units are subsequently attached by conventional means to a tobacco segment on either end, wrapped, and cut in half to form a filter cigarette. Despite the fact that the filter rods so manufactured contain a substantial amount of salvaged filter fibers in some instances they are found to demonstrate an excellent porosity integrity and filter action when applied as a filter unit in the manufacture of filter tip cigarettes.

What is claimed is:

1. In a machine for producing a paperless cigarette filter element in combination,

(a) means for forming a continuous web of filamentary tow into a substantially compact form for movement into a rod-forming means;

(b) said rod-forming means comprising rotating means for shaping and compressing said compact form of filamentary tow moving therethrough into a continuous porous rod while simultaneously introducing a treating fluid into said rod as it is initially shaped and compressed such that the treating fluid penetrates said porous rod to dechannelize the same while maintaining a smooth rod surface, said rotating means comprising a forming zone for shaping and compressing said filamentary tow, said forming zone being defined by the peripheral contact of at least a pair of co-acting rotating peripherally grooved wheels, the grooved peripheral surface thereof being in flow communication with a supply of said treating fluid for introducing said treating fluid into said forming zone defined by said wheels for introduction into said rod of filamentary tow being shaped and compressed within said forming zone whereby said treating fluid penetrates said filamentary tow as it is being shaped and compressed into a continuous porous rod; and

(c) curing means for introducing curing fluid into said porous rod after said rod leaves said rod-forming means.

2. A machine in accordance with claim 1 wherein said treating fluid is supplied through a plurality of jet holes registering with said peripherally grooved surface via passageways provided in said wheels.

3. A machine in accordance with claim 1 wherein said curing means for introducing curing fluid into said porous rod moving therethrough comprises an open ended substantially cylindrical chamber provided with an inner foraminous co-axial tube defining within said cylindrical chamber an internal jacket, said internal jacket being supplied with said curing fluid for application into said porous rod in said foraminous tube.

4. A machine in accordance with claim 1 wherein said grooved peripheral surface is of a porous construction 10 wherein the treating fluid may be caused to issue therethrough via passageways formed within said wheels.

References Cited BENJAMIN A. BORCHELT, Primary Examiner J. J. DEVITT, Assistant Examiner US. Cl. X.R. l3l267;156180 

